The present disclosure relates to a hanger system for connecting a casing hanger to a wellhead. More particularly, the present disclosure relates to a seal assembly implemented in conjunction with connecting a casing hanger to a wellhead.
Various types of seal assemblies have been devised for sealing between a casing hanger and a wellhead. Some seal assemblies are suitable for either high temperature or high pressure application, but not both high temperature and high pressure applications. Other seal assemblies are only suitable for modest temperature and pressure applications. Other seal assemblies initially form a seal, but over time lose their sealing effectiveness.
U.S. Pat. No. 7,096,956 discloses a downhole tool for activating a seal assembly, the entirety of which is incorporated herein by reference. In addition, U.S. Pat. No. 6,202,745 discloses a casing hanger positioned within a wellhead, the entirety of which is incorporated herein by reference.
Most downhole wellhead-hanger seal assemblies are manufactured from two or more components which make up the seal body. The seal body supports one or more seals that seal with the wellhead and the casing hanger. In many cases, these components are interconnected by threads, which inherently allow axial travel between components. The axial travel between seal body components results in wear on both the seals and the sealing surfaces. Additionally, high seal setting forces are conventionally difficult to transmit through a seal body with threaded components.
Another significant problem with prior art sealing assemblies is that when fluid pressure is applied from below the set seal assembly, the interior wellhead wall expands radially outward, and the exterior hanger wall contracts radially inward, thereby creating a significant increase in the radial gap, which inherently detracts from sealing effectiveness. The disadvantages of this created gap are particularly significant when high downhole pressure is applied from below the seal assembly.
The disadvantages of the prior art are overcome by the methods and systems disclosed herein which are generally directed to an improved seal assembly and lockdown method of implementing the same.
While embodiments of this disclosure have been depicted and described and are defined by reference to exemplary embodiments of the disclosure, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.